1. Field of the Invention:
This invention relates to cameras and more particularly to a contact device in a camera.
2. Description of the Related Art:
FIG. 6 is a back elevational view of a typical example of the conventional camera with its back cover opened. In the drawing, a camera body 1 has a back cover 2 pivotally mounted thereto by a hinge portion 3. In the camera body 1 there are a film cartridge chamber 4, a picture frame portion (aperture) 5, a film takeup spool chamber 6 containing a spool 7 and a sprocket 8, a film windup lever 9 and a finder peep window (eyepiece) 10.
In the back cover 2 of the camera, there are a leaf spring 11 as a presser for the loaded film cartridge, a film presser plate 12, and a roller 13 for pressing the film against the spool 7, all arranged on the inner surface of the back cover 2.
In this example of the camera, a date printing system (not shown), for example, is provided behind the film presser plate 12. From this reason, a date imprinting window portion 14 is formed in the upper corner of the film presser plate 12. The provision of the date imprinting system or the like to the camera back cover 2 side is itself known publicly. 15a, 15b, 16a, and 16b are contact elements of circuit terminals arranged respectively on the camera body 1 side and the cack cover 2 side in order to perform electrical intercommunication between a control circuit (not shown) in the camera body 1 and the functional mechanism (or circuit) (not shown) provided in the camera back cover 2. The contact elements 15a and 15b on the camera body side are provided in the lower side portion of the camera body 1 as laterally arranged. The contact elements 16a and 16b of the back cover 2 are arranged in symmetric positions to the contact elements 15a and 15b of the camera body 1 respectively with respect to the axis of the hinge portion 3.
So, when the back cover 2 is closed on the camera body 1, the contact elements 16a and 16b of the back cover 2 touch the contact elements 15a and 15b of the camera body 1 respectively, and they are electrically connected to each other. Thus, an electrical connection is made between the control circuit in the camera body 1 and the functional system in the back cover 2.
By the way, recently, the camera back cover or interchangeable back cover tends not only to have the date imprinting function but also to be made of multiple function by adding, for example, a function of printing desired data, and further a command function of specifying shooting conditions such as the interval time and the number of frames to be automatically shot, and a setting function of exposure conditions such as arbitrary setting of a program line graph in the programmed mode. For this reason, the communication between the camera body and the back cover becomes complicated. This leads to increase the number of contact elements for communication between them.
To lay out the required number of contact elements for communication on the camera body 1 side and the back cover 2 side, if they are arranged in accordance with the layout of the above-described conventional camera of FIG. 6, the number of contacts increases, such as that shown in FIG. 7. That is, assuming that, for what is shown in FIG. 6, two contact elements are added to each of the camera body 1 and the back cover 2, namely, the contact elements 15c, 15d, 16c, 16d are added, then the additional contact elements must be arranged as shown in FIG. 7, or the additional contact elements 15c and 15d of the camera body 1 side are arranged in the lower side portion of the camera body 1 in a horizontal row adjacent to the contact elements 15a and 15b, or, due to space limitations, for example, on the portion above the film cartridge chamber 4 as the contact elements 15c' and 15d'. In accordance with this, the contact elements 16c and 16d (16c' and 16d') of the back cover 2 side are arranged in the corresponding positions to the contact elements 15c and 15d (15c' and 15d') of the camera body 1 side respectively.
However, such a contact element layout as shown in FIG. 7 has the following drawbacks:
(1) As can be said generally on the points of contact of the contact elements, in order to prevent poor contact of the point of contact, it is required for the contact element to have a self-cleaning effect. In the case of the contact elements of the back cover side, due to the closing locus of the back cover, the nearer the contact element arranged to the axis of rotation of the back cover, the higher the self-cleaning effect obtained. Therefore, in the contact element arrangement of lateral one row, the farther the contact element from the axis of rotation of the back cover, the weaker the self-cleaning effect becomes, and, therefore, a greater possibility of poor electrical contact occurs.
(2) In the conventional example, the layout of the contact element arrangement is influenced by the limited internal space of the camera. For this reason, the contact elements may be arranged in separate areas quite apart from each other with the difficulty of fabrication and the number of assembly steps being increased. As a result, production cost is increased. Also, in some cases, it may require a height increase in the camera.
Now, for information, an example of the conventional circuit with which the above-described contact elements are used is given in FIG. 8.
A circuit 1' in the camera body 1 includes a battery 107, a control circuit 108 for the camera connected in parallel to the battery 107, a buzzer 112 connected in parallel to the battery 107 through a resistor 111, and a transistor 110 for driving the buzzer 112. The collector-emitter path of the transistor 110 is connected across the buzzer 112, and its base is connected to the control circuit 108 through a resistor 109 and also to the negative terminal of the battery 107 or a connection terminal 104a for ground, through a resistor 113. A normally open switch 114 is arranged to turn on when a camera release is actuated, and is connected between the control circuit 108 and the connection terminal 104a. Also, the base of the transistor 110 is connected to a connection terminal 106a for display. That pole of the switch 114 which is connected to the control circuit 108 is connected to a connection terminal 105a for triggering a data imprinter.
A data imprinting circuit 2' incorporated in the back cover 2 includes a battery 127, a data imprinting control circuit 115 connected in parallel to the battery 127 and having another terminal which is connected to a connection terminal 105b for trigger, the negative terminal of the battery 127 being connected to a connection terminal 104b for ground, and light emitters 116 such as LEDs with their segment terminal groups being connected to the control circuit 115 and their common terminal Cm being connected to the connection terminal 104b for ground through a transistor 118, the base of the transistor 118 being connected to a terminal C of the control circuit 115 through a resistor 117.
A battery checking circuit 121 is connected in parallel to the battery 127 through a transistor 120. A monostable multivibrator 122 is connected to the output of the checking circuit 121. 123 is also a monostable multivibrator which is connected to the terminal C of the control circuit 115. The pulse width of the monstable multivibrator 123 is shorter than that of the monostable multivibrator 122. Also, the base of the transistor 120 is connected to the common terminal Cm of the light emitters 116 through a resistor 119, and to the positive terminal of the battery 127 through a resistor 144.
A NOR gate 125 is connected to the output of the monostable multivibrator 122 and through an inverter 124 to the output of the monostable multivibrator 123. An astable multivibrator 126 is connected to the output side of the NOR gate 125 and through a resistor 128 and a diode 129 to a connection terminal 106b for display. When the input of the astable multivibrator 126, or the output of the NOR gate 125, is high level, the oscillation of the vibrator 126 stops.
In operating the circuit comprised of the above-described members, when release of the camera body 1 is carried out, the switch 114 turns on, causing the connection terminals 105a, 105b to become low level. Responsive to this signal of low level, the control circuit 115 starts an imprinting operation by driving the light emitters 116 and changing and maintaining the terminal C to and at high level for a time T.sub.0 necessary to the imprinting.
Then, the transistors 118 and 120 turn on to energize the light emitters 116, thereby the imprinting is performed, and at the same time the checking circuit 121 also operates.
If, at this time, the voltage of the battery 127 is higher than the checking voltage V.sub.BAT of the battery, in other words, the voltage obtained by subtracting the voltage drop Vz due to the constant voltage diode 132 from the voltage of the battery 127 and dividing it by the resistors 130 and 135 as appearing across the resistor 135 is higher than the voltage V.sub.BE across the base-emitter path of the transistor 137, because the transistor 137 turns on, the output, e, of the checking circuit 121 remains low, and the monostable multivibrator 122 does not operate.
Meanwhile, the monostable multivibrator 122 responsive to the falling edge of the pulse from the terminal C of the control circuit 115 produces a pulse which takes low level for a constant time T.sub.1 determined by the time constant of the resistor 142 and capacitor 143. That is, a pulse which is high or the time T.sub.1 is produced at the output, g, of the inverter 124. As a result, the output, h, of the NOR gate 125 becomes a pulse of low level with the width T.sub.1. Thus, during the time when the output, h, of the NOR gate 125 is low level, the astable multivibrator 126 oscillates at a frequency, f, determined by the resistor 144 and capacitor 145, and this oscillation causes the transistor 110 in the camera body 1 to turn on and off repeatedly and the buzzer 112 to produce a sound.
In other words, each time the printing operation has been carried out and the light emission terminates, the buzzer 112 produces a sound for the constant time T.sub.1.
In case when the voltage of the battery 127 is lower than the check voltage V.sub.BAT, despite the fact that the checking circuit 121 is supplied with current, the transistor 137 does not turn on. Therefore, the capacitor 139 connected between the output of the checking circuit 121 and the connection terminal 104b for ground is charged through the resistor 131. When the output, e, of the checking circuit 121 exceeds the threshold voltage V.sub.TH of the input side of the monostable multivibrator 122, the monostable multivibrator 122 then operates, producing a pulse of duration T.sub.2 determined by the time constant of the resistor 140 and the capacitor 141.
At this time, similar to the case when the voltage of the battery 127 is higher than the check voltage V.sub.BAT, the pulse of width T.sub.1 appears at the output, g, of the inverter 124. But, the output, h, of the NOR gate 125 becomes low only for the time equal to the pulse width T.sub.2, and the buzzer 112 produces a sound for the time T.sub.2.